Xiaojing Liu: Sustainable Development of Agriculture in Saline Soil Areas

The Effect of Freezing Saline Water Irrigation in Winter on the Reclamation of Saline Soils

Xiaojing Liu, Xiumei Zhang, Xiangjun Li, Renzhao Mao, Zhixia Xie, Lilin Yang and Jin Xu

The frozen point is varied in different salinity water. When melting saline ice, the meltwater at initial thawing stage contains more salt while at late thawing stage contains less salt. The high salinity water infiltrates fast in saline soils than low salinity water.When irrigating saline soils with saline water which will be frozen to ice in cold winter,during the thawing period in spring, the initial melted high salinity water infiltrates firstly and then the late melted low salinity water (even fresh water) which would wash out the deposit salts and create a desalinized soil surface layer. Based on the principle of water desalinization by natural freezing, combined with the seasonal dynamics of soil salinity,infiltration of saline water and crop salt tolerance, a new method was innovated for reclaiming and utilizing saline soils. The key technology of this method is freezing saline water irrigation in winter combined with the integrate management of saline soils such as drainage and plastic mulching etc.

In 2008, this method was applied to reclaim the coastal saline soils in Haixing county of Hebei province. When prepared the land, drainaging tubes or reed bundles were set in 40 cm soil depth with 8 m distance. 11 g l-1 saline groundwater with 180 mm irrigation quantity was applied in January 17 to 25, 2008. After the saline ice melted, the land was mulched by plastic film. No freezing saline water irrigation and no plastic mulching were as CK. Cotton, sunflower and Kosteletzkya virginica were grown in that land. Results showed that the soil salts content in 0-20 cm soil depth was decreased from 0.84% before irrigation to 0.45% after melted water infiltrated into soil in spring, while that the no freezing irrigation CK was increased from 0.71% to 1.33% (Figure 1a). The soil salts content in 0-20cm soil depth at sowwing stage in freezing saline water irrigation with plastic mulching after saline ice melted was 0.35% while that no mulching was 0.77% (Figure 1b). When sowwing crops, emergence rate was higher than 90% in cotton, sunflower and Kosteletzkya virginica in freezing saline water irrigation combine with plastic

mulching treatments and seedlings grew well. There was almost no emergence in no freezing saline water irrigation and no plastic mulching (Figure 2).